Liquid crystal displays of recent years are characterized by achieving low power consumption, thinness and light weight and thus have been in wide use as displays for a computer, a cellular phone, a PDA, and a video game machine. A typical liquid crystal display includes a liquid crystal display panel and a backlight by which the liquid crystal display panel is illuminated from its rear surface. The liquid crystal display panel is constituted by sandwiching a liquid crystal layer between an active matrix substrate and a counter substrate.
The active matrix substrate is constituted by forming a plurality of pixels in matrix form on a glass substrate. Further, in the case where a color display is performed, generally, one pixel is composed of three sub-pixels. Each of the sub-pixels is provided with a TFT and a pixel electrode. Moreover, the counter substrate includes a counter electrode and a color filter that are provided on a glass substrate. The color filter has colored areas of red (R), green (G), and blue (B) colors, which are in one-to-one correspondence with the sub-pixels.
In the liquid crystal display of this type, a voltage applied between each of the pixel electrodes and the counter electrode is controlled so that the transmittance of the liquid crystal layer is controlled with respect to each of the sub-pixels. As a result of this control, an image is displayed on a display screen by means of illumination light from the backlight that has been transmitted through the liquid crystal layer and each of the colored areas.
With respect to the conventional liquid crystal displays having the above-described function of displaying an image, there recently has been proposed a liquid crystal display that also has a function of capturing an image (see, for example, Patent Document 1). In the liquid crystal display disclosed in Patent Document 1, a plurality of photodiodes are formed in matrix form on an active matrix substrates and a liquid crystal display panel functions as an area sensor.
Furthermore, in Patent Document 1, PIN diodes of a lateral structure are used as the photodiodes. Using the processes of forming a TFT, each of the PIN diodes is formed by providing a p layer, an i layer, and an n layer in this order on a silicon film that is used also for the TFT. Further, on a backlight side of each of the PIN diodes, generally, a light-blocking film is provided in order to prevent illumination light from a backlight from being incident on the each of the PIN diodes.
Patent document 1: JP 2006-3857 A